Generally, imagewise exposed silver halide black-and-white photographic materials are processed by processing steps such as black-and-white development, fixing, rinse, etc., and imagewise exposed silver halide color photographic materials (hereinafter referred to as color photographic materials) are processed by processing steps such as color development, desilverization, rinse, stabilization, etc. Imagewise exposed silver halide reversal color photographic materials are processed by processing steps such as black-and-white development and reversal development followed by color development, desilverization, rinse, stabilization, etc.
In the color development step, exposed silver halide grains are reduced by color developing agents to form silver and at the same time, the thus formed oxidant of the color developing agent reacts with a coupler to form a dye image.
In the subsequent desilverization step, developed silver formed in the development step is oxidized by bleaching agents having an oxidizing effect into silver salt (bleaching). Unused silver halide is converted by fixing agents into soluble silver salt (fixing). Thus, the developed silver and the unused silver halide is removed from the sensitive layers. Bleaching and fixing can be carried out independently by a bleaching step and a fixing step, respectively. Alternatively, bleaching and fixing can be simultaneously carried out as a bleach-fixing step. The details of these processing steps and the compositions of processing solutions, etc. are described in James, The Theory of Photographic Process, fourth edition (1977), Research Disclosure No. 17643, pages 28-29, ibid. No. 18716 (page 651 left column to right column) and ibid. No. 307105 (pages 880-881).
In addition to the above-described basic processing steps, various auxiliary steps such as a rinse step, a stabilization step, a hardening step and a stop step are carried out to retain the photographic and physical qualities of the dye image.
The above-described processing steps are generally conducted in automatic processors. Photographic processing is conducted by various laboratores ranging from large-scale laboratories provided with large-size automatic processors to more recent photo shops (called mini-laboratories) using small-size automatic processors in the shop. Thus, there is a possibility that processing performance is adversely affected.
The incorporation of metal ions into the processing solutions is a major cause of reduced processing performance. For example, when processing solutions are prepared, metal ions such as calcium, magnesium and iron contained in water, or metal ions such as calcium dissolved out from photographic materials, are incorporated into the processing solutions. Such metal ions have an adverse effect on processing performance.
For example, in a developer, when calcium ion or magnesium ion is accumulated, these metal ions react with ingredients such as carbonates in the processing solution to form a precipitate or sludge, and the precipitate or the sludge is deposited onto the processed film, whereby staining or the clogging of the filters of the processor results. Transition metal ions, typically iron ion, often greatly reduce the storage property of the processing solution. As a result, a lowering in image density and a lowering in photographic performance such as rise in fog result. In other cases, there is a possibility that metal ions are left behind in the processed films and as a result, image stability is deteriorated.
Further, when a transition metal such as iron ion is mixed into a bleaching solution using hydrogen peroxide or persulfate, the stability of the solution is remarkably lowered and the problems such as bleach inferior arise.
In the case of a fixing solution, on the other hand, the stability is lowered when a transition metal salt is mixed into the conventional thiosulfate-containing fixing solution, and further, turbidity and sludge are formed in the solution. As a result, various problems such as the reduction of the circulating flow rate due to the clogging of filter in automatic developing machine, fixing failure, and processing stain of film arise.
Furthermore, in the case of a stabilizing solution prepared by using a hard water containing a large amount of potassium and magnesium, the solution may have turbidity due to the formation of bacteria therein and cause the stain of film. When a transition metal type ion such as iron ion is mixed into the solution, the preservability of film after processing is deteriorated since the ion remains in the film.
Accordingly, there is a need in the art to solve the problems caused by such metal ions.
As a method for solving the above-described problems, the use of chelating agents for sequestering the metal ions has been proposed. Examples of the chelating agents conventionally used include amino polycarboxylic acids (e.g., ethylenediaminetetraacetic acid, diethylenetriaminepentaacetic acid, etc.) as described in JP-B-48-30496 (the term "JP-B" as used herein means an "examined Japanese patent publication") and JP-B-44-30232, organic phosphonic acids as described in JP-A-56-97347 (the term "JP-A" as used herein means an "unexamined published Japanese patent application"), JP-B-56-39359 and West German Patent 2,227,639, phosphonocarboxylic acids as described in JP-A-52-102726, JP-A-53-42730, JP-A-54-121127, JP-A-55-126241 and JP-A-55-65956, and the compounds described in JP-A-58-195845, JP-A-58-203440 and JP-B-53-40900.
Some of the above described compounds are practically useful, but these compounds are not considered to provide satisfactory performance. For example, when ethylenediaminetetraacetic acid is added to a developing solution, it accelerates the decomposition of the developing agent or preservative in the developing solution in the presence of iron ion. Furthermore, photographic characteristics are deteriorated. For example, a lowering in image density and rise in fog result, even though the acid has a high ability for sequestering calcium ion. Alkylidene-diphosphonic acids do not have such a deteriorating effect in the presence of iron ion, but when these acids are added to a processing solution prepared using hard water containing a relatively large amount of calcium, the solids which are formed result in maintenance and operational difficulties of the automatic processor and other problems.
There is a tendency to increasingly reduce the replenishment rate of photographic processing solutions in light of environmental concerns. Hence, the residence time of the processing solutions in the processors is prolonged such that preservation of the processing solutions is highly desirable. Accordingly, there is a need to develop an excellent novel chelating agent which is free of the problem caused by accumulated metal ions in the developing solution and which effectively sequester metal ions.
The above-described processing steps have been conducted in shops provided with small-size automatic processors (called mini-laboratories) in recent years. Accordingly, rapid processing attention to customers has become increasingly important.
However, the iron(III) complex salt of ethylenediaminetetraacetic acid conventionally used has a fundamental disadvantage in that the oxidizing power thereof is low. Bleaching accelerators (e.g., mercapto compounds described in U.S. Pat. No. 1,138,842) are added to improve the oxidizing power. However, rapid bleaching cannot be achieved.
Red prussiate, iron chloride, bromates, etc. are known as bleaching agents capable of achieving rapid bleaching. However, red prussiate cannot be widely used due to environmental concerns. Iron chloride is inconvenient to handle, because it corrodes metals. Bromate solutions are unstable.
Accordingly, there is a need to provide a bleaching agent which is easy to handle, is free from the problem of the discharge of waste liquor and achieves rapid bleaching.
Iron(III) complex salt of 1,3-diaminopropanetetraacetic acid has been proposed as a bleaching agent meeting the above requirements in recent years.
However, this bleaching agent causes bleach fog. The addition of buffering agents to the bleaching agent has been proposed as a method for reducing the bleach fog (see, JP-A-1-213657). However, the problem is not be sufficiently solved by this method. Particularly, in rapid processing wherein color development is conducted in a short time of within 3 minutes, high-activity developing solutions are used which result in a much greater degree of bleach fog.
Furthermore, when processing solutions having a bleaching ability with iron(III) complex salt of 1,3-diaminopropanetetraacetic acid are used, stain is increased during storage after processing.
Furthermore, when continuous processing is carried out by using the processing solutions having a bleaching ability with iron(III) complex salt of 1,3-diaminopropanetetraacetic acid, desilverization performance is greatly lowered in comparison with that at the early stage of continuous processing and precipitates are formed. Therefore, there is a need to provide a novel processing composition having a bleaching ability which solves the above described problems and a processing method which can be used in place of conventional processing methods.